Yesterday Morning (9th May 2020), I had good discussion with Sundaresan Krishnaswami on " Contract Testing ". I thank Sundaresan for his time and sharing his knowledge. It started with an example: The Owner provides the house or Place of Residence to the Tenants. "Rent Agreement" is provided for the house and It contains agreement to use the house. The house comes with like kitchen, living room, bed room, fans, geysers etc.. It also contains who resides and what is the contractual period, obligation (money) etc.. Here, Owner is the Server and Tenant is Client. Client-Server Architecture. Illustrating the same in the E-Commerce Context: In Some Development Companies, There can be two teams developing the Payments and Orders APIs. In B2B or B2C Ecommerce applications, we place an order using web browser through payment methods and Order is created. Order is successful only when Payment is successful. In general, Payments te